This is regarding the ending of Assassin's Creed: Brotherhood. I have marked the question below as a spoiler, so please do not hover over it if you haven't played through the game yet!

At the end of the game, Desmond is forced to kill Lucy. Prior to him stabbing her, you basically button-mash until he makes the strike. Is there an alternate ending or a way to avoid killing her, such as a sequence of buttons to break free?

For context, I have only recently finished Brotherhood, and have not begun Revelations yet, so I'd appreciate any answers that avoid future-game content.